1. Field of the Invention
The present invention relates to the field of moving pictures, and more particularly, to an apparatus and method for recording and/or reproducing state information associated with audio for moving pictures, and a recording medium for storing audio state information.
2. Description of the Related Art
Development in the field of digital compression techniques and increases in the capacity of recording mediums are now enabling moving picture information to be compressed into digital data and recorded. Compression techniques include a variety of standards. In the case of video, the MPEG (moving picture experts group)-2 video (ISO/IEC 13818-2) MP@ML (Main Profile at Main Level) standard, which has the same image quality as current analog televisions, is now the most widely used. The use of the MPEG-2 MP@HL (Main Profile at High Level) standard, which is capable of achieving the image quality of high definition television (HDTV) is rapidly increasing. In the case of audio, AC (Audio Coding)-3 is generally used around North America, and MPEG1/2 Audio (ISO/IEC13818-3) standard is being used in Europe. The amount of audio data is less than that of video data, so that the linear pulse coded modulation (LPCM) standard, in which there is no compression can also be used for audio.
In this way, audio data and video data are signal-processed in accordance with respective standards, and then combined into data of a bitstream. At this time, the MPEG-2 System (ISO/IEC 13818-1) standard is generally used. That is, each of the audio data and the video data is packeted, and discrimination information for discriminating between audio and video, buffer control information, and timing information for synchronizing an audio signal with a video signal, are added to each packet. Timing information related to a clock signal to be used by a decoder is also added to each packet, resulting in pack data. Here, the digital versatile disc (DVD) video standard prescribes that the size of one pack of data is 2048 bytes.
A general moving picture recording apparatus includes several important functions among which there is an after recording function of later replacing and overwriting only an audio portion among moving picture data which has already been recorded on a recording medium. Existing analog recording mediums have tracks on which video signals for moving pictures and audio signals are separately recorded, such that the after recording function is easily performed. Also, an analog signal is not recorded in a particular recording unit, so that operations required for the after recording are completed by overwriting a desired portion.
Here, audio which has been originally recorded is called original audio, and audio to be replaced and recorded later is called secondary audio. In order to preserve original audio upon recording of secondary audio, two audio tracks to separately record the original audio and the secondary audio must be prepared. Accordingly, original audio and secondary audio are discriminated from each another by the positions of their tracks.
While the two tracks are simultaneously played back, the secondary audio signal is only output when an audio signal exists in the track for secondary audio, and otherwise, an audio signal existing in the track for original audio is output. In this way, secondary audio which has been partially recorded on a track can be reproduced. When reproduction of only the original audio is desired, an audio signal on the original audio track can be reproduced independently of the existence or non-existence of audio signals on the secondary audio track.
However, in the digital recording medium, audio/video (A/V) signals have been mixed and recorded on a recording area in a predetermined recording unit without classification, such that recording and reproducing of secondary audio using the overwriting method used by the analog recording medium is not possible.